Soil moisture and ground thaw state are both indicative of a hillslopes ability to transfer water. In cold regions in particular, it is widely known that the wetness of surface soils and depth of ground thaw are important for runoff generation, but the diversity of interactions between surface soil moisture and ground thaw themselves has not been studied. To fill this knowledge gap, detailed shallow soil moisture and thaw depth surveys were conducted along systematic grids at the Baker Creek Basin, Northwest Territories. Multiple hillslopes were studied to determine how the interactions differed along a spectrum of topological, typological and topographic situations (T³ template). Results did not show a simple relationship between soil moisture and ground thaw as was expected. Instead, correlation was a function of wetness such that the correlation between soil moisture and ground thaw improved with site wetness. To understand why differences in soil moisture and ground thaw state arose, water and energy fluxes were examined for these subarctic study sites to discern the key processes controlling the patterns observed. Results showed that the key control in variable soil moisture and frost table interactions among the sites was the presence of surface water. At the peatland and wetland sites, accumulated water in depressions and flow paths maintained soil moisture for a longer duration than at the hummock tops. These wet areas were often locations of deepest thaw depth due to the transfer of latent heat accompanying lateral surface runoff. Although the peatland and wetland sites had large inundation extents, modified Péclet numbers indicated that the relative influence of external and internal hydrological processes at each site were different. Continuous inflow from an upstream lake into the wetland site caused advective and conductive thermal energies to be of equal importance to ground thaw. The absence of continuous surface flow at the peatland and valley sites led to the dominance of conductive thermal energy over advective energy for ground thaw. A quantitative explanation for the shallow soil moisture-ground thaw patterns was provided by linking hydrological processes and hillslope storage capacity with the calculated water and energy fluxes as well as the modified Péclet number. These results suggest that the T³ template and the modified Péclet number could be very useful parameters for differentiating landscape components in modeling soil moisture and frost table heterogeneity in cold regions.

Based on the ‘free radical theory of aging,’ I hypothesized that hypoxia caused by the mammalian dive response induces free radical production which could modulate or accelerate cellular aging. On the other hand, to prevent free radical “stress” (pro- /antioxidant imbalance), divers could display elevated protective mechanisms. Additionally, the unusual connection between diving physiology and foraging ecology implies that aging physiology is significant to our understanding of ecology for divers. This study examines three aspects of aging in representative diving mammals. First, gracilis muscle morphology was analyzed for old/young shrews (water shrew, Sorex palustris (diver); short-tailed shrew, Blarina brevicauda (non-diver)). Extracellular space was elevated in old animals (10% diver, ~70% non-diver; P=0.021), which corresponded to a larger extracellular collagen component of old muscle (~60%; P=0.008). Muscle was dominated by Type I collagen, and the ratio of collagen Type I: III more than doubled with age (P=0.001). Second, oxidative stress markers, protective antioxidant enzymes and apoptosis were examined in muscle of the two shrew species. The activities of antioxidant enzymes catalase and glutathione peroxidase were statistically identical at each age in both species. The Cu,Zn superoxide dismutase isoform was, however, elevated in older animals (115% diver, 83% non-diver, P=0.054). Only one indicator of oxidative stress (lipid peroxidation) increased with age (P=0.009), whereas the other markers declined (4-hydroxynonenal content, P=0.008, dihydroethidium oxidation, P=0.025). Apoptosis occurred in <1% of myocytes, and did not change with age. On balance, diving water shrews did not have adaptations to combat oxidative stress, yet they do not display excessive oxidative tissue damage. Apoptosis was similar between species. The third study component was the development of a predictive simulation model for the energetics of old/young foraging Weddell seals, Leptonychotes weddellii. With advancing age, the model predicts declining net energy gain associated with a decrease in muscle contractile efficiency. The effects of age are exacerbated when good prey patches are scarce. In such cases, declines in old seal energy gain caused by increased buoyancy and decreased aerobic dive limit become apparent. The model also addresses the idea that behavioral plasticity may allow older animals to compensate for age-related performance constraints.

No description available.

The primary objectives of this study were to address how stream temperature is influenced by (1) spatial variability in energy exchanges, (2) reach-scale stream-subsurface water interactions and (3) the net radiation dynamics associated with standing dead riparian vegetation. Stream temperature, riparian microclimate, and hydrology were characterized for a 1.5 km reach of Fishtrap Creek, located north of Kamloops, British Columbia. Within-reach air temperature and humidity variability was small, while wind speed, net radiation and surface-subsurface interactions exhibited considerable spatially variability. The field data were used to drive a deterministic energy budget model to predict stream temperature. The model was evaluated against measured stream temperature and performed well. The model indicated that the spatially complex hydrology was a significant control on the observed stream temperature patterns. A modelling exercise using three canopy cover scenarios revealed that post-disturbance standing dead trees reduce daytime net radiation reaching the stream surface by one third compared to complete vegetation removal. However, standing dead trees doubled daytime net radiation reaching the stream compared to pre-wildfire conditions. The results of this study have highlighted the need to account for the spatial variability of energy exchange processes, specifically net radiation and surface-subsurface water interactions, when understanding and predicting stream thermal regimes.

No description available.

No description available.

The primary objectives of this study were to address how stream temperature is influenced by (1) spatial variability in energy exchanges, (2) reach-scale stream-subsurface water interactions and (3) the net radiation dynamics associated with standing dead riparian vegetation. Stream temperature, riparian microclimate, and hydrology were characterized for a 1.5 km reach of Fishtrap Creek, located north of Kamloops, British Columbia. Within-reach air temperature and humidity variability was small, while wind speed, net radiation and surface-subsurface interactions exhibited considerable spatially variability. The field data were used to drive a deterministic energy budget model to predict stream temperature. The model was evaluated against measured stream temperature and performed well. The model indicated that the spatially complex hydrology was a significant control on the observed stream temperature patterns. A modelling exercise using three canopy cover scenarios revealed that post-disturbance standing dead trees reduce daytime net radiation reaching the stream surface by one third compared to complete vegetation removal. However, standing dead trees doubled daytime net radiation reaching the stream compared to pre-wildfire conditions. The results of this study have highlighted the need to account for the spatial variability of energy exchange processes, specifically net radiation and surface-subsurface water interactions, when understanding and predicting stream thermal regimes.

Thesis (M.Sc.)--Memorial University of Newfoundland. / Typescript. Bibliography: l. 76-80. Also available online.

Thesis (M.S.)--University of Hawaii, 1966. / Bibliography: leaves [14]-16.

Thesis (Ph. D.)--Massachusetts Institute of Thechnology / Woods Hole Oceanographic Institution, 1980. / Grant no: OCE 76-81190. Photocopy of typescript. Includes bibliographical references (p. 92-98).